This invention relates to a process for producing a low sulfur content fuel oil in a high yield by three steps of (1) a hydrogen treatment, (2) a pyrolysis treatment, and (3) a desulfurizing treatment.
2. DESCRIPTION OF THE PRIOR ART
In recent years, a rapidly increasing demand for fuel oils having a low sulfur content has existed in order to prevent environmental pollution. With a view toward providing low sulfur content fuel oils, an indirect desulfurizing method and a direct desulfurizing method have been employed, but neither of these methods has ever proved entirely satisfactory. Since the indirect desulfurizing method comprises removing asphalt from a vacuum distillation oil or a residual oil, desulfurizing the resulting oil, and mixing the desulfurized oil with a vacuum distillation residual oil, the sulfur content of the mixed fraction is naturally restricted. On the other hand, the direct desulfurizing method is a hydrodesulfurizing method at high temperatures and pressures, and therefore, many problems remain to be solved from the standpoint of chemical engineering and the method is not economically feasible. Economically, it is extremely difficult to use these methods to treat high sulfur content crude oils occurring in Khafji or Kuwait to form fuel oils having a sulfur content of not more than 1%. Accordingly, development of methods has been desired for producing low sulfur fuel oils which conform to the pollution control regulations that will become more rigorous in the future in order to prevent environmental pollution.